On 26/09/2019 14:22, GB wrote:
I have a concealed cistern behind MDF, which has been tiled.

I am fitting a new flush valve in place of the old syphon. It's mostly
done, but I need to recess the button. That needs a 40mm hole through
the tiles and MDF, in place of the existing rather ragged 30-35mm hole.

What's the best way of doing that? 40mm drill will tend to wander. I
have a 1/2" belt sander, but that'll take ages. Any suggestions please?

https://www.permagrit.com/small-rotary-tools/

These willl take down tiles as well as MDF
(wear a mask)

Or

https://www.permagrit.com/radius-ext...e-file-coarse/

Permagrit tools are ruddy brilliant actually



--
I would rather have questions that cannot be answered...
....than to have answers that cannot be questioned

Richard Feynman